Ooo this is so tricky! It largely depends on you as a couple as to what you like and who you are as people, however, what I've seen too is that since Pinterest and Instagram there are identifiable trends that seem to do the rounds and inspire people. The most important thing is that whatever you choose, it's you. After all the day is about celebrating the two of you!
You need a wedding theme as it sets the tone and the bigger picture of the day ahead. It can help with deciding on the dress, or dresses, colours, decor, budget and ambience. It can be on trend or uniquely you as a couple. It can be themed to your favourite genre of movies or music, or it can just be a mix of all of that.
If you're not sure what to go for then start with you as a team and these questions:
How did you meet? Maybe there's something around there that creates a story for your day.
What are your joint interests? If you both love golf then that might be an idea for the theme of the day.
How do you decorate where you live? Maybe you're into minimalism or enjoy lots of bright and bold decorations.
What's your budget? Sometimes a theme will suit a specific venue better than another, do you have the budget to hire the right venue.
What colours do you like? Always a good starting place for a theme, however, just make sure they're not too obscure or you might struggle with decor to match the theme.
DIY wedding or hired planner? Who is doing the wedding will largely guide how the decor might look, as it's alot easier to make hessian bunting for a rustic theme than it is to make a glass chandelier for a ballroom theme!
When is your wedding? Season will dictate the kind of flowers you can get and maybe even the decorations, however, don't let that stop you. My hubby and I love Christmas and even though we didn't have a fully Christmas themed wedding in May, we borrowed bits from Christmas that we love and embedded them into our day (the colours, warm candle and fairy lights, a christmas song first dance by Michael Buble, and I bought little baubles in the January sales as the gift for guests).
There's something to get you started and thinking! Most weddings these days that I've photographed seem to be equally about the couple, not just the bride like in the old days, so it's best to integrate the 2 of you into the day.